Downhole Electric Driven Pump Unit

ABSTRACT

A downhole electric driven pump unit for oil production comprises a submersible electric motor ( 1 ), a driven oil pump ( 2 ), a working plunger pump ( 4 ), an oil tank ( 7 ) provided with a secondary oil filter ( 8 ), an oil volume expansion compensator ( 9 ) and a hydraulic engine ( 10 ). Above-piston and under-piston cavities ( 11, 12 ) of the hydraulic engine cylinder ( 13 ) are connected to the oil pump suction and discharge sides ( 15, 16 ) through a distributor ( 14 ). The hydraulic engine piston ( 17 ) is connected to the plunger ( 18 ) of the working pump. The electric motor is provided with a protector ( 19 ) and is cinematically linked with the driven pump shaft by means of the protector shaft. The working pump cylinder ( 20 ) is provided with a sealed cylindrical diaphragm ( 21 ) made of elastic material such that oil filled cavity ( 22 ) is formed. The working pump plunger ( 18 ) is mounted such that it is reciprocatingly displaceable in the cavity ( 22 ). A pressure valve ( 31 ) is arranged above the discharge valve ( 6 ) such that a cavity ( 23 ) is formed. The compensator ( 6 ) is in the form of a cylinder ( 24 ) provided with a cylindrical diaphragm ( 25 ) which is placed therein such that an internal sealed cavity ( 26 ) communicating with the oil tank ( 7 ) and an annular cavity ( 27 ) is formed. Said invention makes it possible to increase the performance factor and reliability of the unit.

The invention applies to the field of mechanical engineering, particularly to well pumps for extracting oil.

PREVIOUS TECHNOLOGY

Electric hydraulically actuated diaphragm well pump for extracting oil (see Patent RU No. 2062906, Class F 04 B 47/06, Jun. 27, 1996).

The known design has shortcomings of low efficiency, short service life for the flexible plane diaphragm due to high stroke frequency, low pump lift performance, inability to extract oil with low water cut due to the suction valves' poor carrying capacity.

The closest technical solution is the electric hydraulically actuated well pump consisting of a submersible electric motor, engine-driven oil pump, plunger working pump with suction and pressure valves, oil tank with fine media oil filters, oil expansion joint and hydraulic motor. Head-piston and bottom-piston cylinder chambers of the hydraulic motor are connected through the control valve to the suction and pressure sides of the oil pump (the latter of which is equipped with a safety valve), and a hydraulic motor piston connected to the working pump plunger (see Patent RU No. 2166668, Class F 04 B 47/08, May 10, 2001). The drawback of this design is wear and tear of the working pump plunger seals, which decreases the pump's capacity and lift performance.

DISCLOSURE OF INVENTION

The invention is intended to solve the problem of increasing working pump service life and pump lift performance and capacity. The technical result achieved by solving said problem is increasing efficiency and operating reliability of the electric hydraulically actuated well pump.

The stated problem is solved and the technical result is achieved due to the fact that the electric hydraulically actuated well pump consists of a submersible electric motor, engine-driven oil pump, plunger working pump with suction and pressure valves, oil tank with fine media oil filters, oil expansion joint and hydraulic motor. Head-piston and bottom-piston cylinder chambers of the hydraulic motor are connected through the control valve to the suction and pressure sides of the oil pump, (the latter of which is equipped with a safety valve), and the hydraulic motor piston is connected to the working pump plunger. The electric motor is equipped with a protector, the shaft of which kinematically connects the electric motor shaft to the shaft of the engine-driven oil pump. An axial piston pump is used as the engine-driven oil pump, and the plunger working pump cylinder is equipped with a hermetic cylindrical flexible diaphragm, which forms a chamber filled with oil. The working pump plunger is capable of reciprocal motion within this chamber, and a lift valve is installed over the plunger working pump pressure valve to form a chamber. The oil expansion joint is made in the form of a cylinder, within which is a flexible cylindrical diaphragm forming an internal hermetic chamber connected to the oil tank and an annular chamber surrounding the flexible diaphragm. The oil expansion joint cylinder is equipped with suction and pressure valves; the suction valve is connected on its inlet side with the external space around the pump, and the pressure valve is connected on its exit side by means of a pipe with the chamber between the plunger working pump pressure valve and the lift valve.

The pump can be equipped with additional suction valves, which can be placed coaxially in the cylinder walls of the plunger working pump and oil expansion joint in one or multiple rows. Making the oil expansion joint with suction and pressure valves and connecting it to the chamber between the working pump pressure valve and the lift valves doubles the pump's capacity by pumping oil on the hydraulic motor piston's reciprocal stroke, avoids wear and tear on the working pump plunger seals (as they operate in oil and do not directly contact the pump medium), and increases the pump's lift performance. The pump end effector is a cylindrical diaphragm made of a flexible material such as rubber reinforced with glass fiber or Kevlar, which increases the membrane's durability. The plunger working pump end effector is a hermetic oil-filled chamber bounded by a cylindrical flexible diaphragm, within which the plunger moves reciprocally; this decreases the cyclical load on the diaphragm (as compared with the diaphragm pump indicated above) and thereby increases the plunger working pump's operating reliability. Another advantage of the proposed technical solution is that the pump lift performance and capacity can vary widely by changing the working pump plunger diameter.

Making the pump with additional suction valves increases the pump's carrying capacity and makes the pump design more compact, which is particularly important for installations used in wells.

BRIEF DESCRIPTION OF DESIGNS

FIG. 1 shows a longitudinal section of the electric hydraulically actuated well pump.

FIG. 2 shows the variant of suction valve made with additional suction valves for the electric hydraulically actuated well pump, using the plunger working pump cylinder with suction valves as an example.

PREFERRED EMBODIMENT OF INVENTION

The electric hydraulically actuated well pump consists of submersible electric motor 1, engine-driven oil pump 2, plunger working pump 4 with suction 5 and pressure 6 valves, oil tank 7 with fine media oil filters 8, oil expansion joint 9 and hydraulic motor 10, and head-piston 11 and bottom-piston 12 chambers of cylinder 13, which are connected through control valve 14 to the suction 15 and pressure 16 sides of oil pump 2, (the latter of which is equipped with safety valve 3), and piston 17 of hydraulic motor 10 is connected to plunger 18 of working pump 4. Electric motor 1 is equipped with protector 19, the shaft of which kinematically connects the shaft of electric motor 1 to the shaft of engine-driven oil pump 2. An axial piston pump is used as engine-driven oil pump 2, and cylinder 20 of plunger working pump 4 is equipped with hermetic cylindrical flexible diaphragm 21, which forms chamber 22 filled with oil in cylinder 20. Plunger 18 of working pump 4 is capable of reciprocal motion within chamber 22. Lift valve 31 is installed over pressure valve 6 of plunger working pump 4 to form chamber 23. Oil expansion joint 9 is made in the form of cylinder 24, within which is flexible cylindrical diaphragm 25 forming internal hermetic chamber 26 connected to oil tank 7 and annular chamber 27 surrounding flexible diaphragm 25. Cylinder 24 of oil expansion joint 9 is equipped with suction 28 and pressure 29 valves; suction valve 28 is connected on its inlet side with the external space around the pump, and pressure valve 29 is connected on its exit side by means of pipe 30 with chamber 23 between pressure valve 6 of plunger working pump 4 and lift valve 31. The electric hydraulically actuated well pump is installed on production string 32.

The pump can be equipped with additional suction valves 5 and 28; suction valves 5 and 28 can be placed coaxially in the walls of cylinders 20 and 24 of plunger working pump 4 and oil expansion joint 9, respectively, in one or multiple rows.

Control valve 14 is connected by pipe 33 and channel 34, respectively, to head-piston chamber 11 and rod-piston chamber 12 of cylinder 13 of hydraulic motor 10.

The mechanical position switch of control valve 14 consists of push rod 35 and stop 36 with spring 37.

The oil leaks through the seals from chamber 22 return to oil tank 7 through pipe 38.

Production string 32 with the pump assembly is lowered into the casing string, which is sunk into the well. Power is supplied to the submersible electric motor through cable 39, which is attached to production string 32 by clamps (not shown). The electric hydraulically actuated well pump operates as follows.

Upon submersion of the pump into the well, the chambers of electric motor 1 with protector 19 and the hydraulic drive system are filled with filtered oil in accordance with the operating temperature specification.

Upon submersion of the pump in the oil reservoir, the extracted fluid flows into the chambers of cylinders 24 and 20 through suction valves 28 and 5, respectively. Under hydrostatic pressure, pressure valves 29 and 6 and lift valve 31 open and the fluid fills production string 32 to the reservoir level.

When electric motor 1 is engaged, engine-driven oil pump 2 begins to operate, supplying oil through control valve 14 to one of the chambers of cylinder 13 of hydraulic motor 10.

If the oil is fed beneath piston 17, plunger 18 moves upward, filling oil chamber 22 and stretching diaphragm 21 under oil pressure, thereby forcing the fluid out of cylinder 20 through pressure valve 6 into chamber 23 and further through lift valve 31 into production string 32. When piston 17 moves upward, the oil in chamber 26 of oil expansion joint 9 decreases by the volume of plunger 18 issuing from cylinder 13 of hydraulic motor 10; therefore, the fluid from suction valve or valves 28 fills chamber 27 of cylinder 24 of expansion joint 9.

The difference between the volume flow of the oil pumped into and expelled by cylinder 13 of hydraulic motor 10 caused by plunger 18 in head-piston chamber 11 is compensated by changing the volume of oil in oil tank 4 and chamber 26 of expansion joint 9, limited by diaphragm 25.

When piston 17 of hydraulic motor 10 moves downward, the volume of oil under diaphragm 25 in chamber 26 increases and the fluid from cylinder 24 moves into production string 32 through pressure valve 29, pipe 30 and lift valve 31.

Cylinder 20 of plunger working pump 4 simultaneously fills with fluid from suction valve or valves 5. When piston 17 of the hydraulic motor reaches the defined upper or lower position, the switch of control valve 14 engages, and the reciprocal stroke is completed and the operating cycle described above repeats.

Control valve 14 is switched upon movement of piston 17 by the action of push rod 35 on the control valve at the piston's extreme positions. Stop 36 with spring 37 prevents the control valve from ‘sticking’ in the middle position because the spring is compressed, holding a certain potential energy, so that it overcomes the stop's resistance and moves push rod 35 and thereby the valve into one of the extreme positions.

The mechanical switch can also have other variations both alone and in combination with the hydraulic control valve commanding the main control valve.

Upon reduction of the dynamic level of well fluid, the security clearance is established at submersible electric motor 1 control station for the electric current corresponding to the maximum allowable level according to the pump depth and power shutoff.

Otherwise, the pump is stocked with an electric motor with regulated revolutions per minute, which are reduced with lower dynamic level and correspondingly lower pump capacity, controlled by an annulus pressure sensor installed in the electric motor.

INDUSTRIAL APPLICABILITY

The invention can be used in the oil extraction industry and other industries where fluids are extracted from wells. 

1. The electric hydraulically actuated well pump consisting of a submersible electric motor, engine-driven oil pump, plunger working pump with suction and pressure valves, oil tank with fine media oil filters, oil expansion joint and hydraulic motor, and head-piston and bottom-piston cylinder chambers, which are connected through the control valve to the suction and pressure sides of the oil pump, (the latter of which is equipped with a safety valve), and a hydraulic motor piston connected to the working pump plunger is unique in that the electric motor is equipped with a protector, the shaft of which kinematically connects the electric motor shaft to the shaft of the engine-driven oil pump. An axial piston pump is used as the engine-driven oil pump, and the plunger working pump cylinder is equipped with a hermetic cylindrical flexible diaphragm, which forms a chamber filled with oil. The working pump plunger is capable of reciprocal motion within this chamber, and a lift valve is installed over the plunger working pump pressure valve to form a chamber. The oil expansion joint is made in the form of a cylinder, within which is a flexible cylindrical diaphragm forming an internal hermetic chamber connected to the oil tank and an annular chamber surrounding the flexible diaphragm. The oil expansion joint cylinder is equipped with suction and pressure valves; the suction valve is connected on its inlet side with the external space around the pump, and the pressure valve is connected on its exit side by means of a pipe with the chamber between the plunger working pump pressure valve and the lift valve.
 2. The electric hydraulically actuated well pump under Clause 1 is unique in that the pump is equipped with additional suction valves placed coaxially in the cylinder walls of the plunger working pump and oil expansion joint in one or multiple rows. 